$().ready(function() {
    $("#login_form").validate({
        rules: {
            username: "required",
            password: {
                required: true,
                minlength: 5
            }
        },
        messages: {
            username: "请输入姓名",
            password: {
                required: "请输入密码",
                minlength: jQuery.format("密码不能小于{0}个字 符")
            }
        }
    });
});